Peroxyacid antimicrobial composition

ABSTRACT

A peroxyacid antimicrobial concentrate and use composition is provided comprising a C 1  to C 4  peroxycarboxylic acid, and a C 6  to C 18  peroxyacid. The combination of these acids produces a synergistic effect, providing a much more potent biocide than can be obtained by using these components separately. Other components can be added to the composition such as hydrotrope coupling agents, stabilizers, etc. An effective antimicrobial use solution is formed at low concentrations when the concentrate composition is diluted with water to a pH in the range of about 2 to 8. Sanitizing of substantially fixed, &#34;in-place&#34; processing lines in dairies, breweries, and other food processing operations is one utility of the composition.

This is a division, of application Ser. No. 07/734,580, filed Jul. 23,1991 U.S. Pat. No. 5,200,189.

FIELD OF THE INVENTION

The invention relates generally to antimicrobial or biocidalcompositions. More particularly, the invention relates to peroxyacidantimicrobial concentrates and use solutions which can sanitize varioussurfaces such as facilities and equipment found in the food processingand food service industries, and various inanimate surfaces in thehealth care industry.

BACKGROUND OF THE INVENTION

Numerous classes of chemical compounds exhibit varying degrees ofantimicrobial or biocidal activity. Antimicrobial compositions areparticularly needed in the food and beverage industries to clean andsanitize processing facilities such as pipelines, tanks, mixers, etc.and continuously operating homogenation or pasteurization apparatus.Sanitizing compositions have been formulated in the past to combatmicrobial growth in such facilities. For example, Wang, U.S. Pat. No.4,404,040, teaches a short chain fatty acid sanitizing compositioncomprising an aliphatic short chain fatty acid, a hydrotrope solubilizercapable of solubilizing the fatty acid in both the concentrate and usesolution, and a hydrotrope compatible acid so that the use solution hasa pH in the range of 2.0 to 5.0.

Peroxy-containing compositions are known for use in the production ofmicrobicidal agents. One such composition is disclosed in Bowing et al.,U.S. Pat. No. 4,051,059 containing peracetic acid, acetic acid ormixtures of peracetic and acetic acid, hydrogen peroxide, anionicsurface active compounds such as sulfonates and sulfates, and water

Peracetic acid has been shown to be a good biocide, but only at fairlyhigh concentrations (generally greater than 100 part per million (ppm)).Similarly, peroxyfatty acids have also been shown to be biocidal, butonly at high concentrations (greater than 200 ppm), such as in thecomposition disclosed in European Patent Application No. 233,731.

Antimicrobial compositions having low use concentrations (less than 100ppm) which effectively kill microbes are particularly desirable. Lowconcentrations minimize use cost, surface corrosion, odor, carryover ofbiocide into foods and potential toxic effects to the user. Therefore, acontinuing need exists to provide such an antimicrobial composition foruse in food processing, food service and health care facilities. Incontrast to the prior art, the composition of the present invention hasthe unique advantage of having antimicrobial or biocidal activity at lowlevel use concentrations.

SUMMARY OF THE INVENTION

The invention is a peroxyacid antimicrobial concentrate and diluted enduse composition comprising an effective microbicidal amount of a C₁ -C₄peroxycarboxylic acid, and an effective microbicidal amount of a C₆ -C₁₈peroxyacid. The concentrate composition can be diluted with a majorproportion of water to form an antimicrobial sanitizing-use solutionhaving a pH in the range of about 2 to 8, with a C₁ -C₄ peroxycarboxylicacid concentration of at least about 10 ppm, preferably about 10 to 75ppm, and a C₆ -C₁₈ peroxyacid concentration of at least about 1 ppm,preferably about 1 to 25 ppm. Other components may be added such as ahydrotrope coupling agent for solubilizing the peroxyfatty acid in theconcentrate form and when the concentrate composition is diluted withwater.

In contrast to the prior art, we have discovered that at a low pH, (e.g.preferably less than 5) C₆ -C₁₈ peroxyacids such as peroxyfatty acidsare very potent biocides at low levels. When used in combination with aC₁ -C₄ peroxycarboxylic acid such as peroxyacetic acid, a synergisticeffect is obtained, providing a much more potent biocide than can beobtained by using these components separately. This means thatsubstantially lower concentrations of biocide can be used to obtainequal cidal effects, leading to lower costs of the product and lesspotential for corrosion.

As the term is used herein, a C₆ -C₁₈ peroxyacid (or peracid) isintended to mean the product of the oxidation of a C₆ -C₁₈ acid such asa fatty acid, or a mixture of acids, to form a peroxyacid having fromabout 6 to 18 carbon atoms per molecule. The C₁ -C₄ peroxycarboxylicacid is intended to mean the product of oxidation of a C₁ -C₄ carboxylicacid, or a mixture thereof. This includes both simple and substituted C₁-C₄ carboxylic acids.

A method of sanitizing facilities or equipment comprises the steps ofcontacting the facilities or equipment with the use solution made fromthe above concentrate composition of the invention at a temperature inthe range of about 4° to 60° C. The composition is then circulated orleft in contact with the facilities or equipment for a time sufficientto sanitize (generally at least 30 seconds) and the composition isthereafter drained or removed from the facilities or equipment.

One aspect of the invention is the novel, antimicrobial concentratecomposition which is capable of being diluted with a major proportion ofwater to form a sanitizing use solution. A further aspect of theinvention is an aqueous antimicrobial sanitizing use solution which isparticularly suited for "in-place" cleaning applications. A furtheraspect of the invention is a method of employing the use solution of theinvention in the cleaning or satirizing of various process facilities orequipment as well as other surfaces.

DETAILED DESCRIPTION OF THE INVENTION

The invention resides in a peroxyacid antimicrobial concentrate and usecomposition comprising an effective microbicidal amount of a C₁ -C₄peroxycarboxylic acid, and an effective microbicidal amount of a C₆ -C₁₈peroxyacid. We have found that combining these acids produces asynergistic effect, producing a much more potent biocide than can beobtained by using these components separately. The concentratecomposition can be diluted with a major proportion of water to form anantimicrobial sanitizing use solution having a pH in the range of about2 to 8. The sanitizing use solution can be used effectively to clean orsanitize facilities and equipment used in the food processing, foodservice and health care industries.

Peracids

The present invention is based upon the surprising discovery that when aC₆ -C₁₈ peroxyacid is combined with a C₁ -C₄ peroxycarboxylic acid, asynergistic effect is produced and greatly enhanced antimicrobialactivity is exhibited when compared to the C₆ -C₁₈ peroxyacid or the C₁-C₄ peroxycarboxylic acid alone. The present blend of a C₆ -C₁₈peroxyacid and a C₁ -C₄ peroxycarhoxylic acid can effectively killmicroorganisms (e.g., a 5 log₁₀ reduction in 30 seconds) from aconcentration level below 100 ppm and as low as 20 ppm of the peracidblend.

A variety of C₆ -C₁₈ peroxyacids may be employed in the composition ofthe invention such as peroxyfatty acids, monoperoxy- ordiperoxydicarboxylic acids, and peroxyaromatic acids. The C₆ -C₁₈peroxyacids employed in the present invention may be structurallyrepresented as follows: R₁ --CO₃ H, wherein R₁ is a hydrocarbon moietyhaving from about 5 to 17 carbon atoms (a C₈ peroxyacid is generallyrepresented structurally as C₇ --CO₃ H). R₁ may have substituents in thechain, e.g., --OH, CO₂ H, or heteroatoms (e.g., --O-- as in alkylethercarboxylic acids), as long as the antimicrobial properties of theoverall composition are not significantly affected. It should berecognized that "R₁ " substituents or heteroatoms may change the overallacidity (i.e., pKa) of the carboxylic acids herein described. Suchmodification is within the contemplation of the present inventionprovided the advantageous antimicrobial performance is maintained.Furthermore, R₁ may be linear, branched, cyclic or aromatic. Preferredhydrocarbon moieties (i.e. preferred R₁ 's) include linear, saturated,hydrocarbon aliphatic moieties having from 7 to 11 carbon atoms (or 8 to12 carbon atoms per molecule).

Specific examples of suitable C₆ -C₁₈ carboxylic fatty acids which canbe reacted with hydrogen peroxide to form peroxyfatty acids include suchsaturated fatty acids as hexanoic (C₆), enanthic (heptanoic) (C₇),caprylic (octanoic) (C₈), pelargonic (nonanoic) (C₉), capric (decanoic)(C₁₀), undecyclic (undecanoic) (C₁₁), lauric (dodecanoic) (C₁₂),trideclic (tridecanoic) (C₁₃), myristic (tetradecanoic) (C₁₄), palmitic(hexadecanoic) (C₁₆), and stearic (octodecanoic) (C₁₈). These acids canbe derived from both natural and synthetic sources. Natural sourcesinclude animal and vegetable fats or oils which should be fullyhydrogenated. Synthetic acids can be produced by the oxidation ofpetroleum wax. Particularly preferred peroxyfatty acids for use in thecomposition of the invention are linear monoperoxy aliphatic fatty acidssuch as peroxyoctanoic acid, peroxydecanoic acid, or mixtures thereof.

Other suitable C₆ -C₁₈ peroxyacids are derived from the oxidation ofdicarboxylic acids and aromatic acids. Suitable dicarboxylic acidsinclude adipic acid (C₆) and sebacic acid (C₁₀). An example of asuitable aromatic acid is benzoic acid. These acids can be reacted withhydrogen peroxide to form the peracid form suitable for use in thecomposition of the invention. Preferred peracids in this group includemonoperoxy- or diperoxyadipic acid, monoperoxy- or diperoxysebacic acid,and peroxybenzoic acid.

The above peroxyacids provide antibacterial activity against a widevariety of microorganisms, such as gram positive (e.g., Staphylococcusaureus) and gram negative (e.g., Escherichia coli) microorganisms,yeast, molds, bacterial spores, etc. When the above C₆ -C₁₈ peroxyacidsare combined with a C₁ -C₄ peroxycarboxylic acid, greatly enhancedactivity is shown compared to the C₁ -C₄ peroxycarboxylic acid alone orthe C₆ -C₁₈ peroxyacid alone.

The C₁ -C₄ peroxycarboxylic acid component can be derived from a C₁ -C₄carboxylic acid or dicarboxylic acid by reacting the acid with hydrogenperoxide. Examples of suitable C₁ -C₄ carboxylic acids include aceticacid, propionic acid, glycolic acid, and succinic acid. Preferable C₁-C₄ peroxycarboxylic acids for use in the composition of,the inventioninclude peroxyacetic acid, peroxypropionic acid, peroxyglycolic acid,peroxysuccinic acid, or mixtures thereof.

The antimicrobial concentrate of the present invention can compriseabout 0.01 to 10 wt-%, preferably about 0.05 to 5 wt-%, and mostpreferably about 0.1 to 2 wt-% of a C₆ -C₁₈ peroxyacid, and about 0.1 to25 wt-%, preferably about 0.5 to 20 wt-%, and most preferably about 1 to15 wt-% of a C₁ -C₄ peroxycarboxylic acid. The concentrate compositionpreferably has a weight ratio of C₁ -C₄ peroxycarboxylic acid to C₆ -C₁₈peroxyacid of about 15:1 to 3:1. The concentrate contains sufficientacid so that the end use solution has a pH of about 2 to 8, preferablyabout 3 to 7. Some acidity may come from an inert acidulant which may beoptionally added (e.g., phosphoric acid).

The peracid components used in the composition of the invention can beproduced in a simple manner by mixing a hydrogen peroxide (H₂ O₂)solution with the desired amount of acid. With the higher molecularweight fatty acids, a hydrotrope coupler may be required to helpsolubilize the fatty acid. The H₂ O₂ solution also can be added topreviously made peracids such as peracetic acid or various perfattyacids to produce the peracid composition of the invention. Theconcentrate can contain about 1 to 50 wt-%, preferably about 5 to 25wt-% of hydrogen peroxide.

The concentrate composition can further comprise a free C₆ -C₁₈carboxylic acid, a free C₁ -C₄ carboxylic acid, or mixtures thereof. Thefree acids will preferably correspond to the starting materials used inthe preparation of the peroxyacid components. The free C₆ -C₁₈carboxylic acid is preferably linear and saturated, has 8 to 12 carbonatoms per molecule, and can also comprise a mixture of acids. The freeC₆ -C₁₈ carboxylic acid and free C₁ -C₄ carboxylic acid can be presentas a result of an equilibrium reaction with the hydrogen peroxide toform the peroxyacids.

Optional Components

Various optional materials may be added to the composition of theinvention to help solubilize the fatty acids, restrict or enhance theformation of foam, to control hard water, to stabilize the composition,or to further enhance the antimicrobial activity of the composition.

The composition of the invention can contain a surfactant hydrotropecoupling agent or solubilizer that permits blending short chain perfattyacids in aqueous liquids. Functionally speaking, the suitable couplerswhich can be employed are non-toxic and retain the fatty acid and theperfatty acid in aqueous solution throughout the temperature range andconcentration to which a concentrate or any use solution is exposed.

Any hydrotrope coupler may be used provided it does not react with theother components of the composition or negatively affect theantimicrobial properties of the composition. Representative classes ofhydrotropic coupling agents or solubilizers which can be employedinclude anionic surfactants such as alkyl sulfates and alkanesulfonates, linear alkyl benzene or naphthalene sulfonates, secondaryalkane sulfonates, alkyl ether sulfates or sulfonates, alkyl phosphatesor phosphonates, dialkyl sulfosuccinic acid esters, sugar esters (e.g.,sorbitan esters) and C₈ -C₁₀ alkyl glucosides. Preferred coupling agentsfor use in the present invention include noctanesulfonate, available asNAS 8D from Ecolab, and the commonly available aromatic sulfonates suchas the alkyl benzene sulfonates (e.g. xylene sulfonates) or naphthalenesulfonates.

Some of the above hydrotropic coupling agents independently exhibitantimicrobial activity at low pH. This adds to the efficacy of thepresent invention, but is not the primary criterion used in selecting anappropriate coupling agent. Since it is the presence of perfatty acid inthe protonated neutral state which provides biocidal activity, thecoupling agent should be selected not for its independent antimicrobialactivity but for its ability to provide effective interaction betweenthe substantially insoluble perfatty acids described herein and themicroorganisms which the present compositions control.

The hydrotrope coupling agent can comprise about 0.1 to 30 wt-%,preferably about 1 to 20 wt-%, and most preferably about 2 to 15 wt-% ofthe concentrate composition.

Compounds such as mono, di and trialkyl phosphate esters may be added tothe composition to suppress foam. Such phosphate esters would generallybe produced from aliphatic linear alcohols, there being from 8 to 12carbon atoms in the aliphatic portions of the alkyl phosphate esters.Alkyl phosphate esters possess some antimicrobial activity in their ownright under the conditions of the present invention. This antimicrobialactivity also tends to add to the overall antimicrobial activity of thepresent compositions even though the phosphate esters may be added forother reasons. Furthermore, the addition of nonionic surfactants wouldtend to reduce foam formation herein, Such materials tend to enhanceperformance of the other components of the composition, particularly incold or soft water. A particularly useful nonionic surfactant for use asa defoamer is nonylphenol having an average of 12 moles of ethyleneoxide condensed thereon, it being encapped with a hydrophobic portioncomprising an average of 30 moles of propylene oxide.

Chelating agents can be added to the composition of the invention toenhance biological activity, cleaning performance and stability of theperoxyacids. For example, 1-hydroxyethylidene-1,1-diphosphonic acidcommercially available from the Monsanto Company under the designation"DEQUEST" has been found to be effective. Chelating agents can be addedto the present composition to control or sequester hardness ions such ascalcium and magnesium. this manner both detergency and sanitizationcapability can be enhanced.

Other materials which are sufficiently stable at the low pH contemplatedby the present composition may be added to the composition to impartdesirable qualities depending upon the intended ultimate use. Forexample, phosphoric acid (H₃ PO₄) can be added to the composition of theinvention. Additional compounds can be added to the concentrate (andthus ultimately to the use solution) to change its color or odor, toadjust its viscosity, to enhance its thermal (i.e., freeze-thaw)stability or to provide other qualities which tend to make it moremarketable.

The composition of the invention can be made by combining by simplemixing an effective amount of a C₆ -C₁₈ peroxyacid such as a peroxyfattyacid with some source of a C₁ -C₄ peroxycarboxylic acid such asperoxyacetic acid. This composition would be formulated with preformedperfatty acid and preformed peroxyacetic acid. A preferred compositionof the invention can be made by mixing a C₁ -C₄ carboxylic acid, a C₆-C₁₈ carboxylic acid, a coupler and a stabilizer and reacting thismixture with hydrogen peroxide. A stable equilibrium mixture is producedcontaining a C₁ -C₄ peroxycarboxylic acid and a C₆ -C₁₈ peroxyacid byallowing the mixture to stand for from one to seven days at 15° C. to25° C. As with any aqueous reaction of hydrogen peroxide with a freecarboxylic acid, this gives a true equilibrium mixture. In this case,the equilibrium mixture will contain hydrogen peroxide, a C₁ -C₄carboxylic acid, a C₆ -C₁₈ carboxylic acid, a C₁ -C₄ peroxycarboxylicacid, a C₆ -C₁₈ peroxyacid, water, and various couplers and stabilizers.

By using the above approach, the composition of the invention can beformulated by merely mixing readily available raw materials, e.g.,acetic acid, hydrogen peroxide and fatty acid. By allowing solution timefor equilibrium to be obtained, the product containing both of theactive biocides is obtained. In varying the ratio of C₁ -C₄ carboxylicacid to C₆ -C₁₈ carboxylic acid, it is easy to vary the ratio of C₁ -C₄peroxycarboxylic acid to C₆ -C₁₈ peroxyacid.

Concentrate and Use Compositions

The present invention contemplates a concentrate composition which isdiluted to a use solution prior to its utilization as a sanitizer.Primarily for reasons of economics, the concentrate would normally bemarketed and the end user would dilute the concentrate with water to ause solution. A preferred antimicrobial concentrate compositioncomprises about 0.01 to 10 wt-%, preferably about 0.05 to 5 wt-%, of aC₆ -C₁₈ peroxyfatty acid, about 0.1 to 25 wt-%, preferably about 0.5 to20 wt-%, of a C₁ -C₄ peroxycarboxylic acid, about 0.1 to 30 wt-% of ahydrotrope coupling agent, and about 1 to 50 wt-% of hydrogen peroxide.Other acidulants may optionally be employed in the composition such asphosphoric acid.

The level of active components in the concentrate composition isdependent upon the intended dilution factor and desired acidity in theuse solution. The C₆ -C₁₈ peroxyacid component is generally obtained byreacting a C₆ -C₁₈ carboxylic acid with hydrogen peroxide in thepresence of a C₁ -C₄ carboxylic acid. The resulting concentrate isdiluted with water to provide the use solution. Generally, a dilution of1 fluid oz. to 4 gallons (i.e. dilution of 1 to 500 by volume) or to 8gallons (i.e. dilution of 1 to 1,000 by volume) of water can be obtainedwith 2% to 20% total peracids in the concentrate. Higher use dilutioncan be employed if elevated use temperature (greater than 20° C.) orextended exposure time (greater than 30 seconds) are also employed.

In its intended end use, the concentrate is diluted with a majorproportion of water and used for purposes of sanitization. The typicalconcentrate composition described above is diluted with available tap orservice water to a formulation of approximately 1 oz. concentrate to 8gallons of water. An aqueous antimicrobial sanitizing use solutioncomprises at least about 1 part per million (ppm), preferably about 2 to10 ppm of a C₆ -C₁₈ peroxyacid, and at least about 10 ppm, preferablyabout 20 to 50 ppm of a C₁ -C₄ peroxycarboxylic acid. The weight ratioof C₆ -C₁₈ peroxyacid to C₁ -C₄ peroxycarboxylic acid ranges from about0.01 to 0.5 parts, preferably about 0.02 to 0.2 parts of C₆ -C₁₈peroxyacid per part of C₁ -C₄ peroxycarboxylic acid. Preferably thetotal peracid concentration in the use solution is less than about 75ppm, and most preferably between about 5 to 50 ppm. Higher levels ofperacids can be employed in the use solution to obtain disinfecting orsterilizing results.

The aqueous use solution can further comprise at least about 1 ppm,preferably about 2 to 20 ppm, of a hydrotrope coupling agent, at leastabout 1 ppm, preferably about 2 to 200 ppm of hydrogen peroxide, and atleast about 1 ppm, preferably about 2 to 200 ppm of a free C₆ -C₁₈carboxylic acid, a free C₁ -C₄ carboxylic acid, or mixtures thereof. Theaqueous use solution has a pH in the range of about 2 to 8, preferablyabout 3 to 7.

Methods of Use

As noted above, the present composition is useful in the cleaning orsanitizing of processing facilities or equipment in the food service,food processing or health care industries. Examples of processfacilities in which the composition of the invention can be employedinclude a milk line dairy, a continuous brewing system, food processinglines such as pumpable food systems and beverage lines, etc. Foodservice wares can also be disinfected with the composition of theinvention. The composition is also useful in sanitizing or disinfectingsolid surfaces such as floors, counters, furniture, medical tools andequipment, etc., found in the health care industry. Such surfaces oftenbecome contaminated with liquid body spills such as blood, otherhazardous body fluids or mixtures thereof.

Generally, the actual cleaning of the in-place system or other surface(i.e., removal of unwanted offal therein) is accomplished with adifferent material such as a formulated detergent which is introducedwith heated water. After this cleaning step, the instant sanitizingcomposition would be applied or introduced into the system at a usesolution concentration in unheated, ambient temperature water. Thepresent sanitizing composition is found to remain in solution in cold(e.g., 40° F./4° C.) water and heated (e.g., 140° F./60° C.) water.Although it is not normally necessary to heat the aqueous use solutionof the present composition, under some circumstances heating may bedesirable to further enhance its antimicrobial activity.

A method of sanitizing substantially fixed in-place process facilitiescomprises the following steps. The use composition of the invention isintroduced into the process facilities at a temperature in the range ofabout 4° to 60° C. After introduction of the use solution, the solutionis circulated throughout the system for a time sufficient to sanitizethe process facilities (i.e., to kill undesirable microorganisms). Afterthe system has been sanitized by means of the present composition, theuse solution is drained from the system. Upon completion of thesanitizing step, the system optionally may be rinsed with othermaterials such as potable water. The composition is preferablycirculated through the process facilities for 10 minutes or less.

The composition may also be employed by dipping food processingequipment into the use solution, soaking the equipment for a timesufficient to sanitize the equipment, and wiping or draining excesssolution off the equipment, The composition may be further employed byspraying or wiping food processing surfaces with the use solution,keeping the surfaces wet for a time sufficient to sanitize the surfaces,and removing excess solution by wiping, draining vertically, vacuuming,etc.

The composition of the invention may also be used in a method ofsanitizing hard surfaces such as institutional type equipment, utensils,dishes, health care equipment or tools, and other hard surfaces. Thecomposition may also be employed in sanitizing clothing items or fabricwhich have become contaminated. The use composition is contacted withany of the above contaminated surfaces or items at use temperatures inthe range of about 4° to 60° C., for a period of time effective tosanitize, disinfect, or sterilize the surface or item. For example, theconcentrate composition can be injected into the wash or rinse water ofa laundry machine and contacted with contaminated fabric for a timesufficient to sanitize the fabric. Excess solution can then be removedby rinsing or centrifuging the fabric. As the term "sanitizing" is usedin the method of the instant invention, it means a reduction in thepopulation numbers of undesirable microorganisms by about 5 powers of 10or greater (i.e., at least 5 orders of magnitude) after a 30 secondexposure time. It is to be emphasized that the instant use solutionprovides cleaning as well as sanitizing performance although its primaryutility is sanitizing. The composition may also be used to achievedisinfection or sterilization (i.e., elimination of all microorganisms)by employing higher levels of peracids in the use solution.

The following Examples are intended to illustrate the above inventionand should not be construed as to narrow its scope. One skilled in theart will readily recognize that these Examples suggest many other waysin which the present invention could be practiced.

EXAMPLE 1

Experiments were conducted to determine the antimicrobial efficacy ofpure peroxyacids. Table I below demonstrates the antimicrobial efficacyof pure peroxyacids at very low levels when exposed to S. aureus and E.coli. The peroxyacids listed in Table I were tested by diluting. them in0.05M citrate buffer made in distilled water and were exposed to thebacteria for 30 seconds at 20° C. As Table I indicates, thediperoxyacids were somewhat less active than the peroxyfatty acids.Peroxydecanoic acid was very effective at very low levels against S.aureus, but higher levels were required to be effective against E. coli.Higher levels were also required at pH 5.

                  TABLE I                                                         ______________________________________                                        Comparison of Cidal Activity of Peroxyacids                                                     Minimum concentration                                                         required for 5-log                                                            reduction (ppm).sup.(a)                                     Peroxyacid    pH        S. aureus                                                                              E. coli                                      ______________________________________                                        Peroxyhexanoic (C.sub.6)                                                                    3.5       15       15                                                         5.0       20       15                                           Diperoxyadipic (C.sub.6)                                                                    3.5       >50      40                                                         5.0       >60      35                                           Peroxyoctanoic (C.sub.8)                                                                    3.5       5         5                                                         5.0       10       15                                           Peroxydecanoic (C.sub.10)                                                                   3.5       3        10                                                         5.0       1        30                                           Diperoxysebacic (C.sub.10)                                                                  3.5       15       15                                                         5.0       10       50                                           ______________________________________                                         .sup.(a) Peroxyacids tested at 5ppm increments, or at 1, 3, and 5 ppm         where appropriate.                                                       

In Table II below, the antimicrobial synergism between the C₂ and C₃peroxyacids when combined with C₈ and C₁₀ peroxyfatty acids is shown. AsTable II shows, there was little or no antimicrobial activity when theC₂ and C₃ peroxyacids and the C₈ and C₁₀ peroxyfatty acids were testedalone. However, when a C₂ or C₃ peroxyacid was combined with a C₈ or C₁₀peroxyfatty acid, the bacterial kill of E. coli multipliedexponentially. These tests were conducted at pH 4.5 or 5, the pH atwhich E. coli is more difficult to kill (see Table II).

                  TABLE II                                                        ______________________________________                                        Synergistic Interaction of Peroxyacids                                        C.sub.2                                                                              C.sub.3                                                                 Peroxy-                                                                              Peroxy- C.sub.8     C.sub.10                                          acetic!                                                                              propionic!                                                                              Peroxyoctanoic!                                                                           Peroxydecanoic!                                                                        Log                                     (ppm)  (ppm)    (ppm)       (ppm)     reduction                               ______________________________________                                        25              0                     0.sup.a                                  0              5                     0.1.sup.a                               25              5                     3.8.sup.a                                      25       0                     0.3.sup.b                                       0       6                     0.1.sup.b                                      25       6                     3.9.sup.b                               30                          0         0.7.sup.a                                0                          6         0.sup.a                                 30                          6         2.6.sup.a                               ______________________________________                                         .sup.a E. coli, pH 5, distilled water                                         .sup.b E. coli, pH 4.5, 500 ppm hard water                               

EXAMPLE 2

A mixture of short chain fatty acids commercially available from EmeryCorporation under the designation "EMERY 658" was employed in producinga sanitizing concentrate composition of the present invention. The"EMERY 658" acid is a mixture of caprylic acid (C₈) and capric acid(C₁₀)- The perfatty acids were prepared by the method of Parker, et al.,J. Amer. Chem. Soc., 77, 4037 (1955) which is incorporated by reference.The perfatty acid component (also containing 34% acetic acid and 10%hydrogen peroxide) was combined with a pre-made solution of 10.42%peracetic acid, a separate amount of acetic acid, water, and ann-octanesulfonate hydrotrope coupler (NAS 8D). The final composition ofthis Example was as listed in Table III.

EXAMPLE 3

A second composition of the present invention was prepared as describedin Example 2, except that caprylic acid (C₈) and capric acid (C₁₀)replaced some of the perfatty acid of Example 2. The concentration ofperacetic acid was 5% while the concentration of perfatty acids wasreduced to 1.5% (See Table III).

EXAMPLE 4

The composition of Example 4 was prepared according to the procedure ofExample 2, except that no peracetic acid or hydrogen peroxide was addedto the composition. The acetic acid component was increased to 39 wt-%and the composition contained 5% perfatty acid (see Table III). Also, achelating agent (Dequest 2010) was added to the composition.

EXAMPLE 5

The composition of Example 5 was prepared the same as Example 4 exceptthat caprylic acid and capric acid were added to the composition inaddition to the percaprylic and percapric acid of Example 4. Thecomposition contained 3.5% fatty acid and 1.5% perfatty acid (see TableIII).

EXAMPLE 6

Example 6 was prepared with only peracetic acid, acetic acid, hydrogenperoxide, and water. No perfatty acids or fatty acids were added to thecomposition of Example 6. The concentration of total peracid was about5% and the acetic acid concentration was about 39% (see Table III).

EXAMPLE 7

Example 7 was prepared the same as Example 5 except that no peracidswere employed, only a mixture of fatty acids and acetic acid was used,along with water, NAS 8D, and Dequest 2010. The composition contained 5%fatty acid (see Table III).

                  TABLE III                                                       ______________________________________                                                Wt-% of Ingredients                                                   Ingredient                                                                              Ex. 2   Ex. 3   Ex. 4 Ex. 5 Ex. 6 Ex. 7                             ______________________________________                                        Peracetic Acid                                                                          50      50      --    --    50    --                                (10.42%                                                                       solution, 34%                                                                 acetic acid,                                                                  10% H.sub.2 O.sub.2)                                                          Acetic Acid                                                                             22      22      39    39    22    39                                Percaprylic Acid                                                                        3.75    1.125   3.75  1.125 --    --                                (C.sub.8)                                                                     Percapric Acid                                                                          1.25    0.375   1.25  0.375 --    --                                (C.sub.10)                                                                    Caprylic Acid                                                                           --      2.625   --    2.625 --    3.75                              (C.sub.8)                                                                     Capric Acid (C.sub.10)                                                                  --      0.875   --    0.875 --    1.25                              NAS 8D    10      10      10    10    --    10                                Water     13      13      45    45    28    45                                Dequest 2010                                                                            --      --      1     1     --    1                                 ______________________________________                                    

Antimicrobial Efficacy of Examples 2-7

The compositions prepared according to Examples 2-7 were tested fortheir antimicrobial efficacy using the testing procedure of the standardA.O.A.C. sanitizing test. All of the samples tested of Examples 2-7 weremade about 1 hour prior to testing. The bacteria used in the testprocedure were S. aureus and E. coli. Distilled water was used to dilutethe concentrate compositions of Examples 2-7 and the composition wasemployed at room temperature. The following neutralizers were employedin the test: 0.1% thiosulfate, peptone, 0.5% K₂ HPO₄, 0.025% catalasefor peracetic acid; chambers for fatty acid; 0.1% thiosulfate, peptone,0.025% catalase for peracetic acid/fatty acid (perfatty acid).

The antimicrobial activity of Examples 2-7 are summarized in Table IV.Examples 2 and 3 were tested using four samples (a,b,c,d) and Examples4-7 were tested using two samples (a,b). As can be seen in Table IV,Examples 2-5 exhibited excellent kill (>log 6) of both S. aureus and E.coli at 50 ppm of peracid. Examples 6 and 7 (containing no perfattyacids) exhibited little or no activity. More specifically, Example 2 wastested at 1,000 and 500 ppm total product (50 and 25 ppm of bothperoxyacetic acid and perfatty acid). At these low concentrations, theperacid combination gave a 6-7 log reduction in the bacterial count.Example 3 was tested at 1,000 and 500 ppm total product, and also had a6-7 log reduction in the bacterial count. At the 500 ppm productconcentration the product corresponds to 25 ppm of peroxyacetic acid and7.5 ppm of perfatty acids. Example 4, at 1,000 ppm of total product (50ppm of perfatty acid), completely killed all bacteria (greater than 7log reduction). Example 5 also resulted in a complete kill using 1,000ppm of total product (15 ppm perfatty acid). Example 6 contained noperfatty acid (only 50 ppm of peroxyacetic acid) and showed no activityagainst S. aureus and poor activity against E. coli. This is due to thefact that peroxyacetic acid is generally not effective at this level,and is generally used at concentrations greater than 100 ppm. Example 7,containing 5% fatty acid (30 ppm) and no perfatty acid at 1,000 ppmtotal product showed no activity toward either organism.

                  TABLE IV                                                        ______________________________________                                                    Test                                                                          Product                                                                       Concen- POAA.sup.1 /POFA.sup.2 /FA.sup.3                               Sam-   tration Concentration   Log.sub.10 Kill                           Ex.  ple    (ppm)   (ppm)      pH   S. aureus                                                                            E. coli                            ______________________________________                                        2    a      1000    50/50/0    3.5  6.13   >7.30                                   b      1000    50/50/0    3.5  6.52   7.30                                    c       500    25/25/0    3.68 6.63   7.00                                    d       500    25/25/0    3.68 6.78   7.30                               3    a      1000    50/15/35   3.52 7.18   7.30                                    b      1000    50/15/35   3.52 6.63   6.90                                    c       500    25/7.5/17.5                                                                              3.68 6.70   6.76                                    d       500    25/7.5/17.5                                                                              3.68 7.18   7.00                               4    a      1000     0/50/0    3.5  >7.18  >7.30                                   b      1000     0/50/0    3.5  >7.18  >7.30                              5    a      1000     0/15/35   3.5  >7.18  >7.30                                   b      1000     0/15/35   3.5  >7.18  >7.30                              6    a      1000    50/0/0     3.49 NMA.sup.4                                                                            3.48                                    b      1000    50/0/0     3.49 NMA    3.80                               7    a      1000     0/0/30    3.46 NMA    NMA                                     b      1000     0/0/30    3.46 NMA    NMA                                ______________________________________                                         .sup.1 POAA = Peroxyacetic Acid                                               .sup.2 POFA = Peroxyfatty Acid                                                .sup.3 FA = Fatty Acid                                                        .sup.4 NMA = No measurable activity                                      

EXAMPLEs 8-11

Examples 8-11 were prepared by substantially the same procedure as theprevious Examples, except that hydrogen peroxide (H₂ O₂) was mixed withacetic acid and C₈ -C₁₀ fatty acids (Emery 658) to make the peracids ofthe composition. Table V summarizes the components and amounts of thevarious compositions of Examples 8-11 which were made.

                  TABLE V                                                         ______________________________________                                        Peracid Test Formulations                                                     Ingredient  Ex. 8  Ex. 9      Ex. 10                                                                              Ex. 11                                    ______________________________________                                        Acetic Acid 44     39         34    49                                        H.sub.2 O.sub.2 (35%)                                                                     40     40         40    40                                        Dequest 2010                                                                               1      1          1     1                                        NAS 8D      10     10         10    10                                        Emery 658    5     10         15    --                                        ______________________________________                                    

Peracid Stability, Cidal Activity of Examples 8-11

Each of Examples 8-11 were tested for peracid stability and cidalactivity using the A.O.A.C. sanitizing test against S. aureus and E.coli at room temperature with the formulations diluted in distilledwater. Tables VI-IX show the cidal activity of each formulation.Generally all of the formulations reached maximum peracid formationwithin about 12 days. All of the formulations obtained about 2.5%peracid except Example 10 (15% fatty acid) which obtained about 11.5%peracid. Table VI summarizes the cidal activity of Example 8 in whichthe composition was measured for cidal activity on the first day up today 33. At 250 ppm of total product, there were about 4-5 ppm ofperfatty acid and about 20 ppm of peracetic acid as determined by carbon13 NMR spectroscopy. The results are summarized in Table VI.

                  TABLE VI                                                        ______________________________________                                        Peracid Stability,                                                            Cidal Activity of Example 8                                                         Peracid Test.sup.(a) Test Ave. Log Reduction                            Day   Percent Concentration                                                                              pH   S. aureus                                                                              E. coli                              ______________________________________                                         1    4.28    250 ppm      3.92 6.28     NMA.sup.(b)                           6    11.00   250 ppm      3.91 >7.38    >7.18                                 8    11.08   250 ppm      3.86 >7.11    >7.12                                12    12.43   250 ppm      3.83 >7.18    6.96                                 15    12.74   250 ppm      3.88 6.83     --                                   33    10.18   250 ppm      3.83 5.18     6.34                                 ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

The cidal activity of Example 9 is summarized in Table VII below. Theperacetic acid concentration at 250 ppm of product was about 20-21 ppmand the concentration of perfatty acid was about 11 ppm. Theconcentration of peracetic acid at 50 ppm of product was about 4 ppm andthe concentration of perfatty acid was about 2 ppm.

                  TABLE VII                                                       ______________________________________                                        Peracid Stability,                                                            Cidal Activity of Example 9                                                         Peracid Test.sup.(a) Test Ave. Log Reduction                            Day   Percent Concentration                                                                              pH   S. aureus                                                                              E. coli                              ______________________________________                                         1    4.88    250 ppm      3.95 >7.60    NMA.sup.(b)                           6    10.62   250 ppm      3.92 >7.38    >7.18                                 8    11.61   250 ppm      3.98 >7.11    >7.12                                12    12.47   250 ppm      3.91 >7.18    >7.23                                15    12.00   250 ppm      3.95 6.95     --                                                 120 ppm      4.18 >7.13    --                                                  50 ppm      4.41 6.39     --                                   33    10.49   250 ppm      3.85 5.20     6.22                                 ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

The cidal activity of Example 10 is summarized in Table VIII below. At250 ppm of product the peracetic acid concentration was about 19 ppm andthe perfatty acid concentration was about 14 ppm.

                  TABLE VIII                                                      ______________________________________                                        Peracid Stability,                                                            Cidal Activity of Example 10                                                        Peracid Test.sup.(a) Test Ave. Log Reduction                            Day   Percent Concentration                                                                              pH   S. aureus                                                                              E. coli                              ______________________________________                                         1    4.84    250 ppm      3.90 >7.60    NMA.sup.(b),                                                                  4.04                                  6    9.81    250 ppm      3.96 >7.38    >7.18                                 8    10.99   250 ppm      3.96 >7.11    >7.12                                12    11.47   250 ppm      3.94 >7.18    >7.23                                15    11.48   250 ppm      3.96 6.83     --                                   33    10.49   250 ppm      3.95 5.25     6.53                                 ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

The cidal activity of Example 11 is summarized in Table IX below. At 250ppm of product there was about 27 ppm of peracetic acid. At 1000 ppm ofproduct there was about 108 ppm of peracetic acid. No fatty acid wasemployed in the composition of Example 11.

                  TABLE IX                                                        ______________________________________                                        Cidal Activity of Example 11                                                        Peracid Test.sup.(a) Test Ave. Log Reduction                            Day   Percent Concentration                                                                              pH   S. aureus                                                                              E. coli                              ______________________________________                                         5    10.95    250 ppm     3.90 NMA.sup.(b)                                                                            NMA                                   7    12.03   1000 ppm     3.50 4.60     >7.12                                11    12.44   1000 ppm     3.49 6.38     6.64                                 14    12.53   1000 ppm     3.50 4.17     --                                   32    10.77   1000 ppm     3.45 4.77     6.44                                 ______________________________________                                         .sup.(a) ppm total product                                                    .sup.(b) No measurable activity                                          

When comparing the formulations containing fatty acid (Tables VI-VIII),poor activity was measured against E. coli one day after beingformulated. Since the total peracid values were low, more fatty acid waspresent and gram negative bacteria tend to be less sensitive than grampositive bacteria to the C₈ -C₁₀ fatty acids. However, as more peraciddeveloped over the days indicated, increased cidal activity against E.coli was observed. Table IX indicates that to obtain acceptable activity(greater than or equal to 5 log reduction) using only peracetic acid,the peracetic acid must be tested over 100 ppm active. Secondly, thisoxidizing compound is more effective against E. coli than S. aureus.

Generally all the formulations containing fatty acid remain stable afterabout 1 month. This was confirmed by repeated testing over time at 250ppm total product for each formulation in which greater than 5 logreductions were measured against S. aureus and E. coli.

EXAMPLEs 12-17

The cidal activity of a two-component system containing both peraceticacid and fatty acid was investigated using the A.O.A.C. sanitizing test.Table X shows the product formulations examined. The test samplesinclude controls showing cidal activity of NAS 8D as well as fatty acidkill against S. aureus. All the samples were tested in distilled water.

                  TABLE X                                                         ______________________________________                                               Wt-% Ingredient                                                        Ingredient                                                                             Ex. 12  Ex. 13  Ex. 14                                                                              Ex. 15                                                                              Ex. 16                                                                              Ex. 17                             ______________________________________                                        Base 1.sup.(a)                                                                         80      80      80    80    --    --                                 Base 2.sup.(b)                                                                         --      --      --    --    80    80                                 NAS 8D   10      --      10    10    10    10                                 Octanoic Acid                                                                          --      --      10    --    --    10                                 Emery 658                                                                              --      --      10    10    --                                       H.sub.2 O                                                                              10      20      --    --    --    --                                 ______________________________________                                         .sup.(a) H.sub.2 O.sub.2, 35%; acetic acid, 35%; Dequest 2010, 1%; H.sub.     PO.sub.4 (85%), 29%.                                                          .sup.(b) Acetic acid, 35%; Dequest 2010, 1%; H.sub.3 PO.sub.4 (85%), 29%;     H.sub.2 O, 35%.                                                          

Table XI shows the activity measurement of each of Examples 12-17 atvarious test concentrations. When testing the peracetic acid formulationof Examples 12 and 13 (having no fatty acid), biocidal activity occurredonly at 100 ppm or greater. Cidal activity (greater than 4 logreduction) was measured at a minimal concentration of 10 ppm peracidwith fatty acid in the system (Example 14). At 10 ppm peracid, thecomposition containing Emery 658 (Example 15) had better activity thanthe system containing only C₈ (octanoic) fatty acid (Example 14). In thefatty acid controls (Examples 16 and 17), the Emery 658 had more cidalactivity than the C₈ fatty acid. At total product test concentrationsequivalent to 10 or 25 ppm peracid, the fatty acid in the system ofExample 16 did not have significant cidal activity. Example 17 did nothave significant cidal activity at any test concentration.

                  TABLE XI                                                        ______________________________________                                        Peracid Cidal Activity Against S. aureus                                                Peracid Concentration                                                                              Test Log.sup.(a)                               Example   (%)     (ppm Peracid)                                                                              pH   Reduction                                 ______________________________________                                        12        7.02     50          2.79 NMA.sup.(b)                                                 100          2.54 5.45                                                        150          2.41 >7.70                                     13        6.25     50          2.76 NMA                                                         100          2.52 4.51                                                        150          2.40 5.84                                      14        9.32     10          3.52 4.22                                                         25          3.16 >7.70                                                        50          2.90 >7.70                                     15        9.73     10          3.50 6.82                                                         25          3.19 7.55                                                         50          2.88 >7.70                                     16        --      --.sup.(c)   3.53 0.70                                                        --.sup.(c-1) 3.18 1.04                                                        --.sup.(c-2) 2.88 4.07                                      17        --      --.sup.(d)   3.51 0.93                                                        --.sup.(d-1) --   0.66                                                        --.sup.(d-2) --   0.97                                      ______________________________________                                         .sup.(a) Average of duplicate testing.                                        .sup.(b) No measurable activity.                                              .sup.(c) Same total product concentration as Example 15 @ 10 ppm peracid      (about 100 ppm product).                                                      .sup.(c1) Same total product concentration as Example 15 @ 25 ppm peracid     (about 250 ppm product).                                                      .sup.(c2) Same total product concentration as Example 15 @ 50 ppm peracid     (about 500 ppm product).                                                      .sup.(d) Same total product concentration as Example 14 @ 10 ppm peracid      (about 100 ppm product).                                                      .sup.(d1) Same total product concentration as Example 14 @ 25 ppm peracid     (about 250 ppm product).                                                      .sup.(d2) Same total product concentration as Example 14 @ 50 ppm peracid     (about 500 ppm product).                                                 

The cidal activity of a peracetic acid/fatty acid system was measuredcomparing freshly made formulations to month-old formulations ofExamples 14 and 15. These formulations are shown in Table XII whichcompares the titration values of month-old formulations to the samefreshly prepared. Table XIII shows the cidal activity of month-old andfresh formulations of Examples 14 and 15.

                  TABLE XII                                                       ______________________________________                                        Peracid Titration Values                                                               Ex. 14  Ex. 15      Ex. 14  Ex. 15                                   ______________________________________                                        Date formulated                                                                          Month-Old Month-Old   Fresh Fresh                                  % H.sub.2 O.sub.2                                                                        2.15      2.07        1.99  1.99                                   % Peracid  5.37      5.35        4.85  4.86                                   % Total O.sub.2                                                                          2.14      2.10        1.96  1.96                                   ______________________________________                                    

                  TABLE XIII                                                      ______________________________________                                        Peracid Cidal Activity Against S. aureus                                              Peracid   Test Concentration                                                                         Test   Log(a)                                  Example (%)       (ppm Peracid)                                                                              Reduction                                      ______________________________________                                        14      5.37      10           3.46   NMA.sup.(b)                             (Month-Old)       25           3.07   >7.48                                   14      4.85      10           3.34   5.07                                    (Fresh)           25           2.97   7.30                                    15      5.35      10           3.52   5.29                                    (Month-Old)       25           3.04   7.24                                    15      4.86      10           3.42   NMA.sup.(c) /                                                                 3.68                                    (Fresh)           25           2.99   7.48                                    ______________________________________                                         .sup.(a) Average of duplicate testing.                                        .sup.(b) No measurable activity.                                              .sup.(c) Duplicate testing in which only one sample exhibited cidal           activity.                                                                

As can be seen from Table XIII, cidal activity in the peraceticacid/fatty acid system occurs at test concentrations as low as 10 or 25ppm peracid. Mixed results occurred at 10 ppm peracid between themonth-old and fresh formulations of Examples 14 and 15, however,increasing the concentration to 25 ppm resulted in a uniform killactivity (>7 log reduction).

An additional test was run to determine how quickly compounds exhibitingcidal activity are formed upon adding fatty acid to a peracetic acidsystem. Examples 12, 15 and 16 were tested. Examples 12 and 15 wereformulated the day before testing and were day-old samples. Another testsample of Example 15 was formulated immediately prior to testing.Example 16 containing Base 2 (no H₂ O₂) was used to show cidal activityfrom the fatty acid at low test concentrations. Table XIV shows thecidal activity of each Example in distilled water against S. aureus.

                  TABLE XIV                                                       ______________________________________                                        Cidal Activity Against S. aureus                                                                ppm        Test Log.sup.(a)                                 Example   Age     Peracid    PH   Reduction                                   ______________________________________                                        12         1 day  50         2.94 NMA.sup.(b)                                                   100        2.71 6.60                                        15         1 day  10         3.68 7.02                                                          25         3.35 >7.20                                       15        fresh   10         3.76 NMA                                                           25         3.32 NMA                                         16        22 days --.sup.(c) 3.74 NMA                                                           --.sup.(d) --   NMA                                         ______________________________________                                         .sup.(a) Average of duplicate testing.                                        .sup.(b) No measurable activity.                                              .sup.(c) Equivalent total product concentration as Example 15 (day old) @     10 ppm peracid.                                                               .sup.(d) Equivalent total product concentration as Example 15 (day old) @     25 ppm peracid.                                                          

The data from Table XIV suggests that the formation of compoundscontaining cidal activity when adding fatty acid to a peracetic acidsystem is not immediate, but does occur within a day. The formation ofcompounds exhibiting cidal activity occurred within a day after addingfatty acid to the peracetic acid system as in Example 15 with cidalactivity occurring at a concentration as low as 10 ppm peracid. Thus,the cidal activity is not due to the mere combination of fatty acid andperoxyacetic acid, but the fatty acid must be converted to the perfattyacid before substantially enhanced cidal activity occurs.

EXAMPLEs 18-22

A two-component system containing peracetic acid and perfatty acid wasformulated and tested to determine its sanitizing activity over just aperacetic acid system. Table XV shows premixes 1 and 2 used in makingthe composition. The premixes were both made with H₂ O₂ (35% solution),acetic acid, Dequest 2010, and with/without H₃ PO4. Premix 1 was madeabout 5 months before premix 2. To each premix was added NAS 8D, a C₈fatty acid or Emery 658 as shown in Table XVI to complete theformulation of Examples 18-21. Example 22 was formulated as a controland had no fatty acid.

                  TABLE XV                                                        ______________________________________                                        Peracid Premixes                                                                             Wt-% Component                                                 Component        Premix 1 Premix 2                                            ______________________________________                                        H.sub.2 O.sub.2 (35%)                                                                          75.0     35.0                                                Acetic acid (glacial)                                                                          24.0     35.0                                                Dequest 2010      1.0      1.0                                                H.sub.3 PO.sub.4 (85%)                                                                         --       29.0                                                ______________________________________                                    

                  TABLE XVI                                                       ______________________________________                                        Perfatty Acid/Peracetic Acid Formulations                                            Wt-% Ingredient                                                                                               (Control)                              Ingredient                                                                             Ex. 18   Ex. 19  Ex. 20 Ex. 21                                                                              Ex. 22                                 ______________________________________                                        Premix 1 80.0     --      80.0   --    --                                     Premix 2 --       80.0    --     80.0  --                                     NAS 8D   10.0     10.0    10.0   10.0  --                                     C.sub.8 Fatty Acid                                                                     10.0     10.0    --     --    --                                     Emery 658                                                                              --       --      10.0   10.0                                         Acetic Acid                                                                            --       --      --     --    24.0                                   (Glacial)                                                                     H.sub.2 O.sub.2 (35%)                                                                  --       --      --     --    75.0                                   Dequest 2010                                                                           --       --      --     --     1.0                                   ______________________________________                                    

Table XVII shows the sanitizing activity measured from each formulationof Examples 18-22 at 50, 100, or 150 ppm peracetic acid against S.aureus.

                  TABLE XVII                                                      ______________________________________                                        Sanitizing Efficacy of Perfatty Acid/                                         Peracetic Acid System vs.                                                     Sanitizing Efficacy of Peracetic Acid System                                         Total    Fatty    Test                                                        Peracid.sup.(a)                                                                        Acid     Concentration                                                                          Test  Log.sup.(b)                           Example                                                                              (Percent)                                                                              (Percent)                                                                              (ppm)    pH    Reduction                             ______________________________________                                        18     7.69     10.0     150      3.53  >7.06                                                          100      3.64  >7.06                                                           50      3.83  >7.06                                 19     11.21    10.0     150      2.71  >7.06                                                          100      2.80  >7.06                                                           50      3.08  >7.06                                 20     9.08     10.0     150      3.64  >7.06                                                          100      3.65  >7.06                                                           50      3.85  >7.06                                 21     10.92    10.0     150      2.68  >7.06                                                          100      2.77  >7.06                                                           50      3.10  >7.06                                 22     10.40    --       150      3.56  7.06                                  (Control)                100      3.68  3.89                                                            50      3.93  NMA.sup.(c)                           ______________________________________                                         .sup.(a) As peracetic acid                                                    .sup.(b) Average of duplicate testing against S. aureus.                      .sup.(c) No measurable activity.                                         

Extremely good kill (>7 log reduction) was obtained with or without H₃PO₄ in the perfatty acid formulations of Examples 18-21. The twocomponent system of C₈ fatty acid or Emery 658 in combination withperacetic acid (Examples 18-21) had significantly better kill than theperacetic acid system alone (Example 22) at a test concentration of 50to 100 ppm. No activity was measured at 50 ppm with the single peraceticacid system of Example 22.

EXAMPLEs 23-26

The effect of alkyl chain length on antimicrobial efficacy of perfattyacids was determined for percaprylic (C₈) acid, percapric (C₁₀) acid anda percaprylic/percapric (3:1) perfatty acid mixture using thecompositions of Examples 23-26 summarized in Table XVIII below.

                  TABLE XVIII                                                     ______________________________________                                                  Wt-% of Ingredient                                                  Ingredient  Ex. 23  Ex. 24    Ex. 25                                                                              Ex. 26                                    ______________________________________                                        Percaprylic  1      --        --    --                                        (C.sub.8) Acid                                                                Percapric   --       1        --    --                                        (C.sub.10) Acid                                                               C.sub.8 + C.sub.10 (3:1)                                                                  --      --         1    --                                        Perfatty Acid                                                                 Acetic Acid 10      10        10    10                                        Water       84      84        84    85                                        NAS 8D       5       5         5     5                                        ______________________________________                                    

The antimicrobial efficacy of Examples 23-26 are summarized in Table XIXbelow. Examples 23-25 were tested using three samples (a, b, c) of 5,10, and 15 ppm of perfatty acid respectively. Example 26, containing noperfatty acid, was diluted to an equivalent formulation of Examples23-25 containing perfatty acid. As can be seen from Table XIX,significant kill occurred at 5 ppm for S. aureus using Examples 23-25.Significant kill occurred against E. coli at 10 ppm of perfatty acid inExamples 23-25. Example 26 (having no perfatty acid) did not produce anykill of either microorganism.

                  TABLE XIX                                                       ______________________________________                                        Antimicrobial Efficacy of Examples 23-26                                                       Perfatty Acid                                                                 Concentration                                                                              Log Kill                                        Example  Sample  (ppm)        S. aureus                                                                             E. coli                                 ______________________________________                                        23       a        5           >7.0      3.6                                            b       10           --      >7.2                                             c       15           --      >7.2                                    24       a        5           >7.0      3.0                                            b       10           --      >7.2                                             c       15           --      >7.2                                    25       a        5           >7.0    <3.0                                             b       10           --      >7.2, 5.5                                        c       15           --      >7.2                                    26       a       --.sup.a     0       --                                               b       --.sup.b     --        0                                     ______________________________________                                         .sup.a Equivalent total product concentration as Examples 23, 24, 25 at 5     ppm perfatty acid.                                                            .sup.b Equivalent total product concentration as Examples 23, 24, 25 at 1     ppm perfatty acid.                                                       

EXAMPLE 27

The antimicrobial activity of percaprylic acid against E. coli wasmeasured at a 30 second exposure at varying pH's. The formulationcontained 94% water, 5% NAS 8D, and 1% percaprylic acid. The formulationwas diluted in a buffer of 0.05M citrate and 0.05M potassium phosphate.The log kill of this formulation at increasing pH's is summarized inTable XX. Samples containing 7 ppm and 25 ppm of percaprylic acid weretested. As Table XX indicates, significant kill at 7 ppm occurred at apH of 3.0. Significant kill levels were maintained at 25 ppm through apH of 7.0.

                  TABLE XX                                                        ______________________________________                                        Antimicrobial Efficacy of                                                     Percaprylic Acid against E. coli                                                       Log Kill (Perfatty                                                                          Log Kill (Perfatty                                     pH       Concentration 7 ppm)                                                                        Concentration 25 ppm)                                  ______________________________________                                        3.0      >7.2          >7.2                                                   5.0      <3.0          >7.2                                                   7.0      <3.0          >7.2                                                   8.9      --            <3.0                                                   9.0      <3.0          --                                                     ______________________________________                                    

EXAMPLES 28-36

The compositions of Examples 28-30 were made to determine thelimitations on cidal activity of compositions containing at least 30%acetic acid. Higher acetic acid formulations were also tested for theircidal activity. The composition of Example 30 was prepared with nocoupler (NAS 8D). The compositional ingredients of Examples 28-30 aresummarized below in Table XXI.

                  TABLE XXI                                                       ______________________________________                                                Wt-% of Ingredient                                                    Ingredient                                                                              Example 28   Example 29                                                                              Example 30                                   ______________________________________                                        Acetic Acid                                                                             30.0         50.0      50.0                                         H.sub.2 O.sub.2 (35%)                                                                   30.0         15.0      15.0                                         Dequest 2010                                                                            1.0          1.0       1.0                                          C.sub.8 Fatty Acid                                                                      4.0          6.0       5.0                                          NAS 8D (Spray                                                                           5.0          5.0       --                                           Dried                                                                         Distilled Water                                                                         30.0         23.0      29.0                                         ______________________________________                                    

The antimicrobial efficacy of Examples 28-30 was determined using theprocedure of the standard A.O.A.C. sanitizing test. The compositions ofExamples 28-30 were diluted with 500 ppm hard water and employed at 25°C. The bacteria used in the test procedure were S. aureus and E. coli,and a TGE plating medium was employed. Exposure time of the compositionsto the bacteria was 30 seconds. The neutralizer employed in the testingprocedure contained 0.1% thiosulfate, 1.0% peptone, and 0.025% catalase.The antimicrobial activity of Examples 28-30 is summarized in Table XXIIbelow.

                  TABLE XXII                                                      ______________________________________                                        Cidal Activity of Examples 28-30                                                                  Log Reduction                                             Formulation                                                                            Concentration                                                                            pH        S. aureus                                                                            E. coli                                  ______________________________________                                        Example 28                                                                             1 oz: 8 gal..sup.a                                                                       4.48      >7.15  >6.89                                             1 oz: 10 gal..sup.b                                                                      4.83      >7.15  >6.89                                             1 oz: 12 gal..sup.c                                                                      5.04      >7.15  6.41                                              1 oz: 14 gal..sup.d                                                                      5.52      >7.15  5.76                                              1 oz: 16 gal..sup.e                                                                      5.94      >7.15  2.95                                     Example 29                                                                             40 ppm Active                                                                            4.16      >7.15  >6.89                                    Example 30                                                                             40 ppm Active                                                                            4.04      >7.15  >6.89                                    ______________________________________                                         .sup.a 54.2 ppm peracid                                                       .sup.b 43.3 ppm peracid                                                       .sup.c 36.1 ppm peracid                                                       .sup.d 31.0 ppm peracid                                                       .sup.e 27.2 ppm peracid                                                  

As Table XXII indicates, very low concentrations of combinations ofperoxyacetic acid and peroxyfatty acid are very effective in killingbacteria. Also, Example 30 showed that the composition of the inventionis antimicrobially effective without a hydrotrope coupler.

The foregoing discussion and Examples are illustrative of the invention.However, since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides wholly in the claims hereinafter appended.

I claim:
 1. An aqueous peroxyacid antimicrobial composition consistingessentially of:(a) at least about 10 parts per million (ppm) of a C₁ -C₄peroxycarboxylic acid; and (b) at least about 1 ppm of an aliphatic C₆-C₁₈ peroxycarboxylic acid; wherein the aqueous composition has a pH inthe range of about 2 to
 8. 2. The aqueous composition of claim 1 whereinsaid C₁ -C₄ peroxycarboxylic acid consists of peroxyacetic acid,peroxypropionic acid, peroxysuccinic acid, peroxyglycolic acid, ormixtures thereof.
 3. The aqueous composition of claim 1 wherein said C₆-C₁₈ peroxycarboxylic acid is a linear aliphatic peroxyfatty acid, or analiphatic monoperoxy- or diperoxydicarboxylic acid.
 4. The aqueouscomposition of claim 3 wherein said peroxyfatty acid has about 8 to 12carbon atoms per molecule.
 5. The aqueous composition of claim 1 whereinsaid C₆ -C₁₈ peroxycarboxylic acid consists of peroxyoctanoic acid,peroxydecanoic acid, monoperoxy- or diperoxyadipic acid, monoperoxy- ordiperoxysebacic acid, peroxybenzoic acid, or mixtures thereof.
 6. Theaqueous composition of claim 1 wherein the weight ratio of said C₁ -C₄peroxycarboxylic acid to said C₆ -C₁₈ peroxycarboxylic acid is about15:1 to 3:1.
 7. An aqueous peroxyacid antimicrobial sanitizingcomposition consisting essentially of:(a) about 10 to 75 parts permillion (ppm) of a C₁ -C₄ peroxycarboxylic acid; (b) about 1 to 25 ppmof a peroxyacid of the structure R₁ --CO₃ H wherein R, comprises alinear, saturated hydrocarbon chain having about 5 to 17 carbon atoms;(c) about 1 to 200 ppm of a hydrotrope coupling agent; and (d) about 2to 200 ppm of hydrogen peroxide;wherein the aqueous composition has a pHin the range of about 3 to
 7. 8. The aqueous composition of claim 7wherein said C₁ -C₄ peroxycarboxylic acid consists of peroxyacetic acid,peroxypropionic acid, peroxysuccinic acid, peroxyglycolic acid, ormixtures thereof.
 9. The concentrate composition of claim 8 wherein saidperoxyacid of (b) is a peroxyfatty acid having about 8 to 12 carbonatoms per molecule.
 10. The aqueous composition of claim 9 wherein saidperoxyfatty acid consists of peroxyoctanoic acid, peroxydecanoic acid,or mixtures thereof.
 11. The aqueous composition of claim 7 wherein saidhydrotrope comprises n-octanesulfonate.
 12. A method of sanitizingsubstantially fixed in-place process facilities comprising the stepsof:(a) introducing into the process facilities the composition of claim1 at a temperature in the range of about 4° C. to 60° C.; (b)circulating the composition through the process facilities for a timesufficient to sanitize the process facilities; and (c) draining thecomposition from the process facilities.
 13. The method of claim 12wherein said composition is circulated through the process facilitiesfor about 30 minutes or less.
 14. The method of claim 12 wherein aftersaid draining of said composition from the process facilities, theprocess facilities are rinsed with potable water.
 15. The method ofclaim 12 wherein the process facilities comprise a milk line dairy. 16.The method of claim 12 wherein the process facilities comprise acontinuous brewing system.
 17. The method of claim 12 wherein theprocess facilities comprises a pumpable food system or beverageprocessing line.
 18. A method of sanitizing or disinfecting a solidsurface or liquid media by bringing the surface or medium into contactwith the composition of claim 1 at a temperature in the range of about4° C. to 60° C. for an effective period of time sufficient to sanitizeor disinfect the solid surface or liquid media.
 19. A process forsanitizing, disinfecting or sterilizing a contaminated surface using aperoxyacid antimicrobial concentrate composition, comprising the stepsof:(a) diluting in an aqueous liquid said antimicrobial concentrate,thereby forming an aqueous antimicrobial solution, said antimicrobialconcentrate consisting essentially of(i) about 0.01 to 25 wt-% of a C₁-C₄ peroxycarboxylic acid; (ii) about 0.01 to 10 wt-% of an aliphatic C₆-C₁₈ peroxycarboxylic acid; wherein said aqueous antimicrobial solutionhas a pH of about 2 to 8; (b) contacting said aqueous antimicrobialsolution with said contaminated surface for a period of time effectiveto sanitize, disinfect, or sterilize said surface.
 20. The process ofclaim 19 wherein said antimicrobial concentrate further consists ofabout 0.1-30 wt-% of a hydrotrope coupling agent capable of solubilizingsaid C₆ -C₁₈ peroxycarboxylic acid in the concentrate and when theconcentrate is diluted with water.
 21. The process of claim 19 whereinsaid C₁ -C₄ peroxycarboxylic acid consists of peroxyacetic acid,peroxypropionic acid, peroxysuccinic acid, peroxyglycolic acid, ormixtures thereof.
 22. The process of claim 19 wherein said C₆ -C₁₈peroxycarboxylic acid consists of peroxyoctanoic acid, peroxydecanoicacid, monoperoxy- or diperoxyadipic acid, monoperoxy- or diperoxysebacicacid, or mixtures thereof.
 23. The process of claim 20 wherein saidhydrotrope coupling agent consists of n-octanesulfonate, a xylenesulfonate, a naphthalene sulfonate, or mixtures thereof.
 24. The processof claim 19 wherein the contaminated surface is an inanimate solidsurface contaminated by a biological fluid comprising blood, otherhazardous body fluids, or mixtures thereof.
 25. The process of claim 19wherein the contaminated surface comprises the surface of food servicewares or equipment.
 26. The process of claim 19 wherein the contaminatedsurface comprises the surface of a fabric.
 27. The composition of claim1 further consisting of an effective amount of a chelating agent forbinding polyvalent metal cations.
 28. The composition of claim 27wherein said chelating agent is 1-hydroxyethylidene-1,1-diphosphonicacid.
 29. The composition of claim 7 further comprising an effectiveamount of a chelating agent for binding polyvalent metal cations. 30.The composition of claim 29 wherein said chelating agent is1-hydroxyethylidene-1,1-diphosphonic acid.
 31. The process of claim 19wherein said antimicrobial concentrate further consists of an effectiveamount of a chelating agent for binding polyvalent metal cations. 32.The process of claim 31 wherein said chelating agent is1-hydroxyethylidene-1,1-diphosphonic acid.